This paper builds on recent conceptual work about associations that is drawn from the new institutional economics. It uses evidence from New Zealand wool broking to indicate the circumstances in which industry associations can operate effectively and in the broader public interest. Through their strong associative capacity and effective specialization of function, wool-broking industry associations developed flexible routines for managing wool auctions, mediated disputes, mitigated opportunism, addressed major market disruptions, and served as a communication channel with government. External pressures and monitoring from other business interests, governments, and a competitive wool market constrained rent-seeking behavior, preventing members from benefiting at the expense of others.